Lapis lazuli
Use: semi-precious stone, prized since antiquity for its intense color.
Habitat: in crystalline marble as a result of contact metamorphism.
Mineralogy
Lapis lazuli is a deep-blue metamorphic rock.
Component:
• Lazurite, most important 25% to 40%, a blue feldspathoid silicate mineral with the formula (Na,Ca)8(AlSiO4)6(S,SO4,Cl)
• Calcite (white)
• Sodalite (blue),
• Pyrite (metallic yellow).
• ± : augite, diopside, enstatite, mica, hauynite, hornblende, nosean, löllingite, geyerite.